1. Field
Embodiments of the present invention relate to an electronic brake system, and more particularly, to an electronic brake system capable of a structure simplification and a precise pressure control.
2. Description of the Related Art
Every vehicle requires a braking ability and thus requires a brake system, and recently, various types of the brake systems have been proposed for realizing stronger and more stable braking forces. Examples of the brake systems include an anti-lock brake system (ABS) which prevents wheel slip during braking, a brake traction control system (BTCS) which prevents driving wheel slip when a sudden acceleration or a rapid acceleration occurs in a vehicle, and an electronic stability control system (ESC) which together with the ABS and BTSC to control a hydraulic pressure of a braking system so that a vehicle is maintained under a stable driving condition, etc.
Such an electronic brake system includes a plurality of solenoid valves for controlling a brake oil pressure transferred to wheel cylinders (referred to as hydraulic brakes or disk brakes) mounted on the wheels of a vehicle, a pair of low pressure accumulators for temporarily storing oil discharged from the wheel cylinders, a motor and a pump for forcibly pumping the oil stored in the low pressure accumulators, a plurality of check valves to prevent a backflow of oil, and an electronic control unit (ECU) for controlling the operations of the solenoid valves and the motor which are compactly built in an oil pressure block formed of aluminum. Further, a hydraulic pressure supply unit is provided and being used, that receives an electrical signal from a pedal displacement sensor for detecting a displacement of the brake pedal responding to the driver's intention to brake when a driver steps on a brake and supplies pressure to the wheel cylinders.
The electronic brake system provided with the above hydraulic pressure supply unit is disclosed as European Patent No. 2520473. According to the disclosure, the hydraulic pressure supply unit is designed to generate a brake pressure by operating a motor according to a pressure on the brake pedal. Here, the brake pressure is generated by converting a rotatory power of the motor to a rectilinear movement to press a piston.
However, in the electronic brake system with the above structure, the arrangement of the plurality of solenoid valves provided to control the pressure transferred to the wheel cylinders is complex, and, in addition, the plurality of solenoid valves are individually operated to control a hydraulic pressure delivered to the wheel cylinder provided in each wheel, thereby increasing the vibration and the noise due to operating the solenoid valves.
Further, since the configuration of the plurality of the solenoid valves and the flow paths for controlling the pressure according to various control modes becomes complex and in addition, the weight and the volume of the system are increased because a motor, a pump, and a low pressure accumulator are provided additionally, the ease of mounting and the efficient use of space are compromised, and vibration and noise due to motor and pump operations are increased.